The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
Presently, it has become apparent that it is quite difficult to diagnose, monitor, and manage metabolic diseases.
An example of a metabolic disease is diabetes mellitus. In diabetes, sufferers generally have abnormally high blood glucose levels due to a reduced production of insulin (referred to as Type 1 diabetes), or have become resistant to the effects of insulin (referred to as Type 2 diabetes), which is secreted by the pancreas to control blood sugar levels.
Various organs of the body, and in particular, the brain, depend on a continual supply of glucose and are vulnerable to any glucose deprivation. Unable to synthesise or store this primary source of energy, the brain is one of the first organs affected by lowered blood glucose levels. Hypoglycaemia develops when rates of glucose entry into the systemic circulation are reduced relative to glucose uptake by tissues. Hypoglycaemia is usually corrected naturally by the combination of a number of defence mechanisms. Initially, a decrease in insulin secretion in response to declining blood glucose levels occurs. As glucose levels continue to fall, a number of redundant glucose counter-regulatory factors are sequentially activated at specific thresholds to ensure sufficient glucose uptake to the brain and other central nervous system tissue metabolism. These counter-regulatory factors include glucagon, epinephrine, growth hormone, cortisol, and other hormones.
Generally, hypoglycaemia may be defined in a physiological context, as a plasma glucose of <3.9 mmol/l (<3.3 mol/l whole blood). Glycaemic thresholds for activation of the anti-insulin neuro-endocrine counter-regulatory response occurs at plasma glucose values of approximately 3.2 to 3.8 mmol/l. Additionally, antecedent hypoglycaemia has been demonstrated to reduce counter-regulatory responses to subsequent hypoglycaemia.
In patients with Type 1 diabetes undergoing intensive insulin therapy, falling plasma glucose concentrations often do not elicit counter-regulatory responses at normal glycaemic thresholds, allowing glucose levels to drop to dangerously low values. After the first few years of diabetes, the glucagon counter-regulatory response to hypoglycaemia becomes deficient. Additionally, in some cases warning symptoms no longer occur, and the episode may lead to serious complications, such as coma and convulsions. This phenomenon is known as hypoglycaemia unawareness. Studies in patients have demonstrated that as few as two episodes of antecedent hypoglycaemia can blunt responses to subsequent hypoglycaemia.
Symptoms of hypoglycaemia arise from the activation of the autonomous central nervous system (autonomic symptoms) and from reduced cerebral glucose consumption (neuroglycopenic symptoms), some of the latter being potentially life threatening. Nocturnal hypoglycaemia is particularly dangerous because sleep reduces and may obscure autonomic counter-regulatory responses, so that an initially mild episode may become severe. The risk of severe hypoglycaemia is high at night, with at least 50% of all severe episodes occurring during that time.
Even with modest insulin elevations, deficient glucose counter-regulation may also lead to severe hypoglycaemia. Regulation of nocturnal glycaemia is further complicated by the dawn phenomenon. This is a consequence of nocturnal changes in insulin sensitivity following growth hormone secretion: a decrease in insulin requirements approximately between midnight and 5 am, followed by an increase in requirements between 5 am and 8 am.
Thus, there is required a system and/or method for determining an abnormality in metabolic function, which overcomes, at least ameliorates one or more disadvantages of existing arrangements, or provides an alternative to existing arrangements.